1. Field of the Invention
The present invention relates to an audio mirror speaker, and more particularly to an audio mirror speaker for reproducing a high fidelity stereo sound field.
2. Related Background Art
In an audio field, a CD (compact disk player) and a DAT (digital audio tape recorder) have been marketed and remarkable improvement of sound quality has been made. However, from a standpoint of high fidelity stereo sound, a high quality audio signal output unit in most systems has a theoretical listening point at only an apex of an isosceles triangle having a bottom side defined by two speakers. Thus, an audio system by which a listener can enjoy the high fidelity stereo sound over a wide area has not yet been spread. This is due to lack of control of a directivity distribution of an acoustic energy at the audio output unit.
The assignee oi the present invention has proposed a speaker system which enables the control of the directivity distribution over a wide area in Japanese Patent Application No. 61-75144 and U.S. Pat. application Ser. No. 07/280,936.
The audio mirror speaker disclosed in the Japanese Patent Application No. 61-75144 and the speaker system disclosed in the U.S. Pat. application Ser. No. 07/280,936 use a cone shaped rotating audio mirror as the audio mirror.
The rotating audio mirror is simple in its principle and the directivity distribution and a relation between the positions of the mirror and a diaphragm and the shapes thereof can be intuitively recognized by a designer. However, in an actual manufacturing stage of the speaker, the rotating audio mirror which determines the directivity distribution requires high precision manufacturing. As a result, the cost increases. Where the directivity is to be changed after the manufacture, a relative position of the diaphragm and the mirror is changed. The directivity can be changed only by sliding the mirror parallel to the vibration plane of the diaphragm. Accordingly, it is not usable where the directivity is to be changed as desired.